According to Bungie´s newest weekly update, Halo 3 beta offers the chance to gamers to record their 1337ness to the Xbox 360 hard-drive. The recording option will, however, not be on par with the one in the finalized version.
Another new feature promised is split-screen multiplayer, but only on one console in the public beta. Formerly rumoured 1080p / 60fps resolution was, however, partly denied. The game supports 1080p upscaling through VGA, Component on the original Xbox 360, and through HDMI using the new Elite 360.